In this work, we make a step towards a simultaneous description of particle phenomenology and cosmology using the same string derived model[1]} within the framework of free-fermionic formulation of four-dimensional (4d) heterotic superstrings[2]}. Although one of the earliest formalisms of realistic string model building, it has the advantage of full calculability in perturbation theory around a vacuum where all moduli except the dilaton are fixed at the fermionic point, characterised by a set of gauge and discrete symmetries. Instead of constructing a new model from scratch, we consider one of the very first successful constructions of the flipped \(SU(5)\times U(1)\)  [1]}, that was already shown to give a remarkable good particle phenomenology [4]}, [5]}, [6]}, [7]} and we study its cosmology. Our analysis can also serve as a proof of concept for a class of 4d string models with similar properties.
